Genetic information, variation and relationships between organisms-Genetic diversity can arise as a result of mutation or during meiosis

Question 1

What does Meiosis produce?

Answer 1

4 genetically different cells, haploid (half the amount of chromosome/DNA)

Question 2

Benefits of Meiosis?

Answer 2

produces gametes which will be used in sexual reproduction in animals & plants
(2 gametes fuse to form a zygote, zygote develops into organisms)

Question 3

Stages of Meiosis?

Answer 3

Interphase/Meiosis I/Meiosis II/Cytokinesis

Question 4

Interphase?

Answer 4

G1: protein synthesis
S: DNA replication (doubles set of DNA)
G2: organelle synthesis

Question 5

Meiosis I?

Answer 5

Prophase I: DNA coils to form chromosomes, nucleus breaksdown, spindle fibres form, crossing over occurs

Metaphase I: homologous pair of chromosomes line up in middle of cell and attach to
spindle fibre via centromere

Anaphase I: spindle fibres pull, homologous pair of chromosomes separate to opposite sides by independent assortment
Telophase I: chromosomes uncoil, nucleus reforms (left with 2 nuclei)

Question 6

Meiosis II?

Answer 6

Prophase II: DNA coils to form chromosomes, nucleus breaksdown, spindle fibres form
Metaphase II: chromosomes line up in middle of cell and attach to spindle fibre via
centromere
Anaphase II: spindle fibres pull, centromere splits, sister chromatids move to opposite sides by independent assortment
Telophase II: chromatids uncoil, nucleus reforms (left with 4 genetically different nuclei)

Question 7

Cytokinesis?

Answer 7

separating cell into 4 (each receives a nucleus and organelles/cytoplasm)

Question 8

How does Meiosis produce Variation?

Answer 8

Crossing Over and Independent Assortment

Question 9

What is crossing over?

Answer 9

occurs in Prophase I of Meiosis I
homologous pairs of chromosomes wrap around each other and swap equivalent sections of chromatids –produces new combination of alleles

Question 10

What is independent assortment?

Answer 10

• in Anaphase I of Meiosis I – the homologous pairs of chromosomes separate
• in Anaphase II of Meiosis II – the chromatids separate
• independent assortment produces a mix of alleles from paternal and maternal
  chromosomes in gamete

Question 11

What happens to Chromosome number in meiosis?

Answer 11

halves (haploid)

Question 12

What is Mutation?

Answer 12

 Change in DNA

 2 types: Chromosome Mutation and Gene Mutation

Question 13

What causes mutation?

Answer 13

random or due to mutagens (e.g. chemicals, radiation)

Question 14

What is a Chromosome Mutation?

Answer 14

 In plants, inherit more than one diploid set of chromosomes – called polyploidy
 In animals, homologous pair of chromosome do not separate in meiosis, so either inherit one extra or one less chromosome – called non-disjunction

Question 15

What is a Gene Mutation?

Answer 15

 a change in the base sequence of DNA

 2 types = substitution and insertion/deletion

Question 16

substitution?

Answer 16

 replace one base for another, changes one triplet code

Question 17

insertion?

Answer 17

adding a base, deletion = removing a base
both insertion/deletion causes frameshift, all the triplet codes after the mutation
changes, so normal polypeptide chain/protein not produced